To provide a method for embedding electronic watermark information in nearly all of vector type map data so as to identify a person having a copyright and to prevent illegal copy.

The method to embed electronic watermark information in vector type map data comprises the steps of: superimposing electronic watermark generating data on the vector type map data, obtaining cross points between the line segments of the vector type map data and the electronic watermark generating data, excluding the electronic watermark generating data while leaving the cross points, and embedding the cross points in the vector type map data as electronic watermark information.